[PATCH 6.4 696/800] bpf, btf: Warn but return no error for NULL btf from __register_btf_kfunc_id_set()

Greg Kroah-Hartman
2023-07-16T20:26:47Z

From: SeongJae Park <sj@kernel.org>

[ Upstream commit 3de4d22cc9ac7c9f38e10edcf54f9a8891a9c2aa ]

__register_btf_kfunc_id_set() assumes .BTF to be part of the module's .ko
file if CONFIG_DEBUG_INFO_BTF is enabled. If that's not the case, the
function prints an error message and return an error. As a result, such
modules cannot be loaded.

However, the section could be stripped out during a build process. It would
be better to let the modules loaded, because their basic functionalities
have no problem [0], though the BTF functionalities will not be supported.
Make the function to lower the level of the message from error to warn, and
return no error.

[0] https://lore.kernel.org/bpf/20220219082037.ow2kbq5brktf4f2u@apollo.legion

Fixes: c446fdacb10d ("bpf: fix register_btf_kfunc_id_set for !CONFIG_DEBUG_INFO_BTF")
Reported-by: Alexander Egorenkov <Alexander.Egorenkov@ibm.com>
Suggested-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/87y228q66f.fsf@oc8242746057.ibm.com
Link: https://lore.kernel.org/bpf/20220219082037.ow2kbq5brktf4f2u@apollo.legion
Link: https://lore.kernel.org/bpf/20230701171447.56464-1-sj@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/bpf/btf.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 72b32b7cd9cd9..25ca17a8e1964 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -7848,10 +7848,8 @@ static int __register_btf_kfunc_id_set(enum btf_kfunc_hook hook,
pr_err("missing vmlinux BTF, cannot register kfuncs\n");
return -ENOENT;
}
- if (kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES)) {
- pr_err("missing module BTF, cannot register kfuncs\n");
- return -ENOENT;
- }
+ if (kset->owner && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES))
+ pr_warn("missing module BTF, cannot register kfuncs\n");
return 0;
}
if (IS_ERR(btf))
--
2.39.2